Relationship between Shock-cell Length and Noise of Jets from Rectangular and Elliptic Disk Nozzles

2009 ◽  
Vol 26 (2) ◽  
Author(s):  
K. Srinivasan ◽  
T.J.S. Jothi ◽  
U.S.P. Shet
Keyword(s):  
Cell Length ◽  
Shock Cell

Noisefield of Underexpanded Notched Circular-Slot Jets

2002 ◽  
Vol 33 (6) ◽  
pp. 9-23
Author(s):  
S.B. Verma ◽  
E. Rathakrishnan
Keyword(s):  
Acoustic Emission ◽  
Aspect Ratio ◽  
Cell Length ◽  
Emission Characteristics ◽  
Far Field ◽  
Shock Cell ◽  
Acoustic Spectrum ◽  
Compression Waves ◽  
Noise Field ◽  
Notch Geometry

The effect of notches on the flow and noise field of jets from circular-slots is experimentally investigated. Three types of slot geometries, namely, semicircular, triangular and square are studied. The results demonstrate that the presence of the notch introduces a slight aspect-ratio in the initial circular-slot geometry so that the notched jet exhibits characteristics, similar to jets exiting from non-circular geometries. At underexpanded condition, additional expansion and compression waves are observed to emanate from the region of notches that modifies the jet development and results in a reduction in the average shock-cell length, which is accompanied by a reduction in far-field shock associated noise. The acoustic spectrum of the radiated shock noise indicates that notch geometry variation strongly alters the acoustic emission characteristics of these jets both in the screech component and broadband shock associated noise.

An experimental and numerical investigation of under-expanded turbulent jets

2004 ◽  
Vol 108 (1081) ◽  
pp. 145-152 ◽  
Author(s):  
A. J. Saddington ◽  
N. J. Lawson ◽  
K. Knowles
Keyword(s):  
Turbulence Model ◽  
Nozzle Exit ◽  
Experimental Studies ◽  
Independent Solution ◽  
Turbulent Jets ◽  
Cell Length ◽  
Cfd Model ◽  
Shock Cell ◽  
Probe Measurements ◽  
Good Agreement

AbstractThe work described here concentrates on under-expanded, axisym-metric turbulent jets issuing into quiescent conditions. Under-expanded turbulent jets are applicable to most aircraft propulsion applications that use convergent nozzles. Experimental studies used laser doppler velocimetry (LDV) and pitot probe measurements along the jet centreline. These measurements were made for two nozzle pressure ratios (2·5 and 4·0) and at various streamwise positions up to 10 nozzle diameters downstream of the nozzle exit plane. A computational fluid dynamics (CFD) model was developed using the Fluent code and utilised the RNG K-ε two-equation turbulence model. A mesh resolution of approximately one hundredth of nozzle exit diameter was found to be sufficient to establish a mesh independent solution.Comparison of the jet centreline axial velocity (LDV data) and pressure ratio (pitot probe data) showed good agreement with the CFD model. The correct number of shock cells had been predicted and the shock strength agreed well between the experiments and numerical model. The CFD model was, however, found to over-predict the shock cell length resulting in a longer supersonic core. There was some evidence, based on analysis of the LDV measurements that indicates the presence of swirl and jet unsteadiness, which could contribute to a shortening of the shock cell length. These effects were not modelled in the CFD. Correlation between the LDV and pitot probe measurements was generally good, however, there was some evidence that probe interference may have caused the premature decay of the jet. Overall, this work has indicated the good agreement between a CFD simulation using the RNG k-ε turbulence model and experimental data when applied to the prediction of the flowfield generated by under-expanded turbulent jets. The suitability of the LDV technique to jet flows with velocities up to 500ms-1has also been demonstrated.

An experimental and numerical investigation of under-expanded turbulent jets

2004 ◽  
Vol 108 (1081) ◽  
pp. 145-152 ◽  
Author(s):  
A. J. Saddington ◽  
N. J. Lawson ◽  
K. Knowles
Keyword(s):  
Turbulence Model ◽  
Nozzle Exit ◽  
Experimental Studies ◽  
Independent Solution ◽  
Turbulent Jets ◽  
Cell Length ◽  
Cfd Model ◽  
Shock Cell ◽  
Probe Measurements ◽  
Good Agreement

AbstractThe work described here concentrates on under-expanded, axisym-metric turbulent jets issuing into quiescent conditions. Under-expanded turbulent jets are applicable to most aircraft propulsion applications that use convergent nozzles. Experimental studies used laser doppler velocimetry (LDV) and pitot probe measurements along the jet centreline. These measurements were made for two nozzle pressure ratios (2·5 and 4·0) and at various streamwise positions up to 10 nozzle diameters downstream of the nozzle exit plane. A computational fluid dynamics (CFD) model was developed using the Fluent code and utilised the RNG K-ε two-equation turbulence model. A mesh resolution of approximately one hundredth of nozzle exit diameter was found to be sufficient to establish a mesh independent solution.Comparison of the jet centreline axial velocity (LDV data) and pressure ratio (pitot probe data) showed good agreement with the CFD model. The correct number of shock cells had been predicted and the shock strength agreed well between the experiments and numerical model. The CFD model was, however, found to over-predict the shock cell length resulting in a longer supersonic core. There was some evidence, based on analysis of the LDV measurements that indicates the presence of swirl and jet unsteadiness, which could contribute to a shortening of the shock cell length. These effects were not modelled in the CFD. Correlation between the LDV and pitot probe measurements was generally good, however, there was some evidence that probe interference may have caused the premature decay of the jet. Overall, this work has indicated the good agreement between a CFD simulation using the RNG k-ε turbulence model and experimental data when applied to the prediction of the flowfield generated by under-expanded turbulent jets. The suitability of the LDV technique to jet flows with velocities up to 500ms-1has also been demonstrated.

CAMBIAL BEHAVIOR WITH REFERENCE TO CELL LENGTH AND RING WIDTH IN PINUS STROBUS L.

1962 ◽  
Vol 40 (8) ◽  
pp. 1057-1062 ◽  
Author(s):  
M. W. Bannan
Keyword(s):  
Inverse Relationship ◽  
Ring Width ◽  
Pinus Strobus ◽  
Growth Patterns ◽  
Cell Length ◽  
Annual Rings ◽  
Forest Types ◽  
Thuja Occidentalis ◽  
Cambial Cells ◽  
Individual Trees

The relationships between width of annual rings, length of wood cells, and frequency of anticlinal (multiplicative) divisions in fusiform cambial cells were studied by reference to trees of various growth patterns. The trees selected ranged from 8 to 20 in. diameter and included both open-grown specimens with branches close to the ground and forest types with tall, slender shafts. Much fluctuation was noted among individual trees, but in general there was, in the peripheral growth, an inverse relationship between length of wood cells and width of annual rings. The frequency of anticlinal divisions in the cambium remained at a more or less uniform rate in trees with rings from 1.5 to 5 mm wide, but rose sharply when ring width fell below 1.3 mm. This was in contrast to the situation observed earlier in Thuja occidentalis where the rise in frequency of anticlinal divisions was slight and occurred only in trees with rings less than 0.3 mm wide.

Mechanical compression alters proteoglycan deposition and matrix deformation around individual cells in cartilage explants

1998 ◽  
Vol 111 (5) ◽  
pp. 573-583
Author(s):  
T.M. Quinn ◽  
A.J. Grodzinsky ◽  
M.D. Buschmann ◽  
Y.J. Kim ◽  
E.B. Hunziker
Keyword(s):  
Morphological Changes ◽  
Dynamic Compression ◽  
Compressive Strain ◽  
Cell Length ◽  
Cartilage Explants ◽  
Proteoglycan Synthesis ◽  
Length Scale ◽  
Mechanical Compression ◽  
Static Compression ◽  
Associated Matrix

We have used new techniques of cell-length scale quantitative autoradiography to assess matrix synthesis, deposition, and deformation around individual chondrocytes in mechanically compressed cartilage explants. Our objectives were to: (1) quantify the effects of static and dynamic compression on the deposition of newly synthesized proteoglycans into cell-associated and further-removed matrices; (2) measure cell-length scale matrix strains and morphological changes of the cell and matrix associated with tissue compression; and (3) relate microscopic physical stimuli to changes in proteoglycan synthesis as functions of compression level and position within mechanically compressed explants. Results indicate a high degree of structural organization in the extracellular matrix, with the pericellular matrix associated with the most rapid rates of proteoglycan deposition, and greatest sensitivity to mechanical compression. Static compression could stimulate directional deposition of secreted proteoglycans around chondrocytes, superimposed on an inhibition of proteoglycan synthesis; these events followed trends for compressive strain in the cell-associated matrix. Conversely, proteoglycan synthesis and pericellular deposition was stimulated by dynamic compression. Results suggest that cell-matrix interactions in the cell-associated matrix may be a particularly important aspect of the chondrocyte response to mechanical compression, possibly involving macromolecular transport limitations and morphological changes associated with fluid flow and local compaction of the matrix around cells.

scholarly journals FK506-binding protein FklB is involved in biofilm formation through its peptidyl-prolyl isomerase activity

2020 ◽  
Author(s):  
Chrysoula Zografou ◽  
Maria Dimou ◽  
Panagiotis Katinakis
Keyword(s):  
Biofilm Formation ◽  
Negative Regulator ◽  
Cell Length ◽  
Wild Type ◽  
Prolyl Isomerase ◽  
Ppiase Activity ◽  
Peptidyl Prolyl Isomerase ◽  
Knock Out ◽  
E Coli ◽  
The Mean

AbstractFklB is a member of the FK506-binding proteins (FKBPs), a family that consists of five genes in Escherichia coli. Little is known about the physiological and functional role of FklB in bacterial movement. In the present study, FklB knock-out mutant ΔfklB presented an increased swarming and swimming motility and biofilm formation phenotype, suggesting that FklB is a negative regulator of these cellular processes. Complementation with Peptidyl-prolyl isomerase (PPIase)-deficient fklB gene (Y181A) revealed that the defects in biofilm formation were not restored by Y181A, indicating that PPIase activity of FklB is modulating biofilm formation in E. coli. The mean cell length of ΔfklB swarming cells was significantly smaller as compared to the wild-type BW25113. Furthermore, the mean cell length of swarming and swimming wild-type and ΔfklB cells overexpressing fklB or Y181A was considerably larger, suggesting that PPIase activity of FklB plays a role in cell elongation and/or cell division. A multi-copy suppression assay demonstrated that defects in motility and biofilm phenotype were compensated by overexpressing sets of PPIase-encoding genes. Taken together, our data represent the first report demonstrating the involvement of FklB in cellular functions of E. coli.

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